Our main objective is to achieve an understanding of decreased mucosal immunity in marginally-malnourished and malnourished children and thus provide a basis for the therapeutic control of this immune deficiency. We will extensively evaluate mucosal immunity in malnourished children by quantitating immunologically active compounds secreted: primarily S-IgA as well as lysozyme, aminopeptidase, IgG and total protein concentration. With our guinea pig model and Guinea Pig Inclusion conjunctivitis we will correlate mucosal disease resistance and the secretory immune response. We plan to measure the effects of vitamin A and/or protein- calorie deficiencies in the young guinea pig by: a) determining changes in resistance to a mucosal infection, Guinea Pig Inclusion conjunctivitis; b) quantitating S-IgA and bactericidal enzymes concentrations in tears; c) modifying a microassay to measure mucosal cellular immunity; d) determining the duration of depressed mucosal immune mechanisms after nutritional therapy.